This invention relates to a housing for a thermal protector device that protects against overheating of a lighting fixture, or the like.
Lighting manufacturers install a commercially available thermal sensor (also called a thermal switch or thermal protector) which will interrupt power to a fixture when temperatures exceed a certain level. The thermal protector is electrically connected with the power circuit for the lighting fixture and, since it is live during operation, must be insulated from contact with other live parts of the lighting fixture. Current designs of a thermal protector housing require labor intensive means of installation and sometimes do not provide a secure means of holding the thermal protector in place. In addition, replacement of a damaged housing often causes the protector to be destroyed.
Reference is made to Steinke U.S. Pat. No. 4,635,172, Jan. 6, 1987, and Wolfe U.S. Pat. No. 4,835,667, May 30, 1989, for examples of the use of thermal protector devices with lighting fixtures. Reference is also made to Yarmark U.S. Pat. No. 4,861,943, Aug. 29, 1989 which also relates to that subject and discloses a particular form of thermal protector housing with some features in common with the present invention but as to which the present invention is an alternative and an improvement.
In Yarmark, a thermal protector housing includes a body having openings at both ends with a trench therein for guiding the thermal protector through the body and with a resilient tab extending from the interior top surface of the body and stops disposed within and near the front of the body for securing the protector to the body. An arm and a pair of legs extend from the bottom of the body to serve as fasteners to clip the body to a flat plate of the lighting fixture which has apertures receiving the arm and pair of legs. While generally effective for securing a thermal protector, such a device does not allow protector replacement without destroying the integrity of the housing.
The descriptions of the foregoing patents are incorporated herein by reference.
By the present invention, a plastic enclosure houses a thermal protector and provides a means of securing a thermal protector to a master enclosure or an element of a lighting fixture. The housing incorporates a novel latching mechanism to secure the thermal protector inside it that not only affords maximum security but also allows removal of the protector and replacement without damage to the housing. The housing is a molded plastic element generally in the form of a hollow sleeve or flattened tube into which the thermal protector can be readily slid. During the sliding of the thermal protector into the sleeve, it engages a camming surface of a spring finger that comprises part of the exterior of the housing. The engagement of the camming surface of the spring finger causes it to move out of the way so the protector can slide past it and is locked in place once past the projecting portion of the camming surface. The spring finger provides positive locking of the protector unit in place. It also allows the protector unit to be removed by merely lifting the spring finger away from the interior of the housing so that the protector unit can be withdrawn without being blocked by the projection on the spring finger.
The housing further has projections or tabs for interlocking with a surface of a lighting fixture. In the preferred forms, the tabs are configured for positive locking with less risk of breakage than in prior designs.
The described spring finger may, in general, be on any exterior surface of the housing sleeve. Providing the spring finger on the upper surface away from the fixture surface allows extra facility in removal of a thermal protector when desired after installation. However, by locating the spring finger on the underside of the surface more positive securement of the protector is provided.
As an option, with the spring finger on the underside of the housing adjacent the surface of the lighting fixture, the tabs can be made just long enough so the housing can be lifted from the surface sufficiently to move the spring finger and release a protector.
This form of the invention that allows replacement of a thermal sensor when the housing is in place on the fixture may be particularly useful when it is desirable to be able to change a thermal sensor to one of a different rating.
It is therefore the case that very good securement of the thermal protector is achieved without depending on a resilient tab protruding downwardly from the top interior wall of the housing and, also, means are provided for easy removal of a thermal protector when desired, such as if one of the tabs breaks upon installation.
In most respects, it is desirable and advantageous merely to have the housing as described without the option of allowing replacement of a thermal sensor once the housing is installed in a fixture. The spring finger on the bottom surface of the housing allows secure retention of the thermal sensor. As such housings are made and installed, they are susceptible to having one or more of the tabs broken off in their installation procedure. In the housings of former design, the thermal sensor is located now in the defective housing which must be withdrawn and discarded. According to the present invention, the housing that is damaged in installation can simply be withdrawn from the fixture and the spring finger lifted to enable removal of the thermal sensor so that it need not be discarded. Without this feature, the housing that has a broken tab would have to be physically cut in order to remove the sensor and extra care would have to be taken not to damage the sensor in that process.
Further details with respect to features achieving objects and advantages of the present invention will be found in the ensuing description.